"We fixed the digital certificate problem and last evening resumed publishing new apps and updates," Brix wrote on the Windows Phone Developer Blog. "It will take a day or two for the repair to fully deploy and newly-published apps to begin appearing in Marketplace again."

"If your app was in the process of being published, you don't need to take any action. We have applied the fix and the app will continue through the certification and publishing workflow as normal," he told developers.

Microsoft estimated the issue affected a "small percentage of the 100,000-plus apps" on the store.

The issue stopped handsets from installing apps or updates published in the last week, according to Microsoft. It affected phones that had been upgraded to Windows Phone 7.5 from an earlier OS, but apparently not those with the later OS pre-installed.

Earlier in August, Microsoft cut the ribbon on the Windows Phone Dev Center, where developers can build, publish and manage apps for Windows Phone 7.5 as well as for the upcoming Windows Phone 8. The company is gearing up for the release of the updated mobile OS, and is looking to build developer backing as it tries to make headway against Android, iOS and even BlackBerry OS.